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  • C07D473/04—Heterocyclic compounds containing purine ring systems with oxygen, sulphur, or nitrogen atoms directly attached in positions 2 and 6 two oxygen atoms
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  • C07D473/14—Heterocyclic compounds containing purine ring systems with oxygen, sulphur, or nitrogen atoms directly attached in positions 2 and 6 two oxygen atoms with radicals containing only hydrogen and carbon atoms, attached in position 1 or 3 with two methyl radicals in positions 1 and 3 and two methyl radicals in positions 7, 8, or 9

Definitions

• the present invention relates generally to the field of phosphodiesterase 4 (PDE4) enzyme inhibition. More specifically this invention relates to selective PDE4 inhibition by novel adenine analogs, methods of preparing such compounds, compositions containing such compounds, and methods of use thereof.
• PDE4 phosphodiesterase 4
• the cyclic nucleotide specific phosphodiesterases represent a family of enzymes that catalyze the hydrolysis of various cyclic nucleoside monophosphates (including cAMP and cGMP). These cyclic nucleotides act as second messengers within cells, and as messengers, carry impulses from cell surface receptors having bound various hormones and neurotransmitters. PDEs act to regulate the level of cyclic nucleotides within cells and maintain cyclic nucleotide homeostasis by degrading such cyclic mononucleotides resulting in termination of their messenger role.
• PDEs cyclic nucleotide specific phosphodiesterases
• PDE enzymes can be grouped into eleven families according to their specificity toward hydrolysis of cAMP or cGMP, their sensitivity to regulation by calcium, calmodulin or cGMP, and their selective inhibition by various compounds.
• PDE 1 is stimulated by Ca 2+ /calmodulin.
• PDE 2 is cGMP-dependent, and is found in the heart and adrenals.
• PDE 3 is cGMP-dependent, and inhibition of this enzyme creates positive inotropic activity.
• PDE 4 is cAMP specific, and its inhibition causes airway relaxation, anti-inflammatory and antidepressant activity.
• PDE 5 appears to be important in regulating cGMP content in vascular smooth muscle, and therefore PDE 5 inhibitors may have cardiovascular activity. Since the PDEs possess distinct biochemical properties, it is likely that they are subject to a variety of different forms of regulation.
• PDE4 is distinguished by various kinetic properties including low Michaelis constant for cAMP and sensitivity to certain drugs.
• the PDE4 enzyme family consists of four genes, which produce 4 isoforms of the PDE4 enzyme designated PDE4A, PDE4B, PDE4C, and PDE4D [See: Wang et al., Expression, Purification, and Characterization of human cAMP-Specific Phosphodiesterase (PDE4) Subtypes A, B, C, and D, Biochem. Biophys. Res. Comm ., 234, 320-324 (1997)]
• PDE4A PDE4A
• PDE4B PDE4C
• PDE4D PDE4D
• PDE4 isoenzymes are localized in the cytosol of cells and are unassociated with any known membranous structures. PDE4 isoenzymes specifically inactivate cAMP by catalyzing its hydrolysis to adenosine 5′-monophosphate (AMP). Regulation of cAMP activity is important in many biological processes, including inflammation and memory. Inhibitors of PDE4 isoenzymes such as rolipram, piclamilast, CDP-840 and ariflo are powerful anti-inflammatory agents and therefore may be useful in treating diseases where inflammation is problematic such as asthma or arthritis. Further, rolipram improves the cognitive performance of rats and mice inlearning paradigms.
• xanthine derivatives such as pentoxifylline, denbufylline, and theophylline inhibit PDE4 and have received considerable attention of late for their cognition enhancing effects.
• cAMP and cGMP are second messengers that mediate cellular responses to many different hormones and neurotransmitters.
• therapeutically significant effects may result from PDE inhibition and the resulting increase in intracellular cAMP or cGMP in key cells, such as those located in the nervous system and elsewhere in the body.
• Rolipram previously in development as an anti-depressant, selectively inhibits the PDE4 enzyme and has become a standard agent in the classification of PDE enzyme subtypes.
• Early work in the PDE4 field focused on depression and inflammation, and has subsequently been extended to include indications such as dementia. [See “The PDE IV Family Of Calcium-Phosphodiesterases Enzymes,” John A. Lowe, III, et al., Drugs of the Future 1992, 17(9):799-807 for a general review). Further clinical developments of rolipram and other first-generation PDE4 inhibitors were terminated due to the side effect profile of these compounds.
• the primary side effect in primates is emesis, while the primary side effects in rodents are testicular degranulation, weakening of vascular smooth muscle, psychotropic effects, increased gastric acid secretion and stomach erosion.
• the present invention relates to novel adenine compounds that inhibit PDE4 enzymes, and especially have improved side effect profiles, e.g., are relatively non-emetic, (e.g., as compared to the previously discussed prior art compounds).
• the present invention relates to novel 9-substituted-2-trifluoromethyladenine compounds that possess PDE4 inhibitory activity.
• the compounds selectively inhibit PDE4 enzymes.
• the compounds of this invention at the same time facilitate entry into cells, especially cells of the nervous system.
• the present invention provides methods for synthesizing compounds with such activity and selectivity as well as methods of (and corresponding pharmaceutical compositions for) treating a patient, e.g., mammals, including humans, requiring PDE inhibition, especially PDE4 inhibition, for a disease state that involves elevated intracellular PDE 4 levels or decreased cAMP levels, e.g., involving neurological syndromes, especially those states associated with memory impairment, most especially long term memory impairment, as where such memory impairment is due in part to catabolism of intracellular cAMP levels by PDE 4 enzymes, or where such memory impairment may be improved by effectively inhibiting PDE4 enzyme activity.
• a patient e.g., mammals, including humans, requiring PDE inhibition, especially PDE4 inhibition, for a disease state that involves elevated intracellular PDE 4 levels or decreased cAMP levels, e.g., involving neurological syndromes, especially those states associated with memory impairment, most especially long term memory impairment, as where such memory impairment is due in part to catabolism of intracellular cAMP levels by PDE 4 enzymes
• the compounds of the invention improve such diseases by inhibiting PDE4 enzymes at doses which do not induce emesis.
• the present invention includes compounds of Formula I:
• R 1 is methyl
• R 2 is not arylalkyl, heteroarylalkyl, 2-(1,2,3,4-tetrahydro)quinolinyl-methyl or C 1-5 -alkyl.
• R 1 is methyl
• R 2 is not arylalkyl, heteroarylalkyl, heterocycle-alkyl or C 1-5 -alkyl.
• R 1 is ethyl
• R 2 is not arylalkyl, heteroarylalkyl, or C 1-3 -alkyl.
• R 1 is H
• R 2 is not arylalkyl, heterocycle or C 1-3 -alkyl.
• R 1 is methoxyethyl
• R 2 is not arylalkyl or heteroarylalkyl.
• R 2 is aryl having 6 to 14 carbon atoms (e.g., phenyl), which is substituted by benzyloxy, —NR 3 R 4 , —CO—NH—SO 2 —R 5 and/or —SO 2 —NH—CO—R 5 .
• R 2 is aryl having 6 to 14 carbon atoms (e.g., phenyl), which is substituted by benzyloxy and/or —NR 3 R 4 .
• R 2 is arylalkyl having 6 to 14 carbon atoms (e.g., phenyl), which is substituted by benzyloxy, —NR 3 R 4 , —CO—NH—SO 2 —R 5 and/or —SO 2 —NH—CO—R 5 .
• R 2 is heteroaryl which is substituted by morpholinyl, piperazinyl, —NR 3 R 4 , —CO—NH—SO 2 —R 5 and/or —SO 2 —NH—CO—R 5 .
• R 2 is heteroarylalkyl which is substituted by morpholinyl, piperazinyl, —NR 3 R 4 , —CO—NH—SO 2 —R 5 and/or —SO 2 —NH—CO—R 5 .
• R 2 is carbocycle, which is a nonaromatic, monocyclic or bicyclic, group having 5 to 14 carbon atoms, which is substituted by —CO—NH—SO 2 —R 5 and/or —SO 2 —NH—CO—R 5 .
• the compounds of formula I are selected from the following compounds:
• R 1 is methyl
• R 2 is not arylalkyl, heteroarylalkyl, 2-(1,2,3,4-tetrahydro)quinolinyl-methyl or C 1-5 -alkyl.
• R 1 is methyl
• R 2 is not arylalkyl, heteroarylalkyl, heterocycle-alkyl or C 1-5 -alkyl.
• R 1 is ethyl
• R 2 is not arylalkyl, heteroarylalkyl, or C 1-3 -alkyl.
• R 2 is aryl having 6 to 14 carbon atoms (e.g., phenyl), which is substituted by benzyloxy and/or —NR 3 R 4 .
• the compounds of formula I′ are selected from the following compounds:
• the compounds of the present invention are effective in inhibiting, or modulating the activity of PDE4 in animals, e.g., mammals, especially humans. These compounds exhibit neurological activity, especially where such activity affects cognition, including long term memory. These compounds will also be effective in treating diseases where decreased cAMP levels are involved. This includes but is not limited to inflammatory diseases. These compounds may also function as antidepressants, or be useful in treating cognitive and negative symptoms of schizophrenia.
• a method of treating a patient e.g., a mammal such as a human
• a disease state e.g., memory impairment, inflammatory diseases, depression, etc.
• administering comprising administering to the patient a compound according to formula I a :
• a method of treating a patient e.g., a mammal such as a human
• a disease state e.g., memory impairment, inflammatory diseases, depression, etc.
• administering comprising administering to the patient a compound according to formula I a′ :
• a method of treating a patient e.g., a mammal such as a human
• a disease state e.g., memory impairment, inflammatory disesases, depression, etc.
• a disease state e.g., memory impairment, inflammatory disesases, depression, etc.
• administering to the patient a compound according to formula I wherein said compound is selected from the following compounds:
• a method of treating a patient e.g., a mammal such as a human
• a disease state e.g., memory impairment, inflammatory disesases, depression, etc.
• administering e.g., administering to the patient a compound according to formula I′ wherein said compound is selected from the following compounds:
• Halogen herein refers to F, Cl, Br, and I. Preferred halogens are F and Cl.
• Alkyl as a group or substituent per se or as part of a group or substituent (e.g., alkylamino, trialkylsilyloxy, aminoalkyl, hydroxyalkyl), means a straight-chain or branched-chain aliphatic hydrocarbon radical having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, especially 1 to 4 carbon atoms.
• Alkyl radicals for R 1 have up to 5 carbon atoms, preferably 1 to 4 carbon atoms, especially 1 to 3 carbon atoms.
• Suitable alkyl groups for R 1 include methyl, ethyl, propyl, isopropyl, butyl, isopropyl and pentyl.
• Other examples of suitable alkyl groups for R 1 include 1-, 2- or 3-methylbutyl, 1,1-, 1,2- or 2,2-dimethylpropyl and 1-ethylpropyl.
• Alkyl radicals for R 2 have up to 12 carbon atoms, preferably 3 to 8 carbon atoms, especially 3 to 6 carbon atoms.
• Suitable alkyl groups for R 2 include those listed above for R 1 as well as hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, 1-, 2-, 3- or 4-methylpentyl, tert-butyl, 1,1-, 1,2-, 1,3-, 2,2-, 2,3- or 3,3-dimethylbutyl, 1- or 2-ethylbutyl, ethylmethylpropyl, trimethylpropyl, methylhexyl, dimethylpentyl, ethylpentyl, ethylmethylbutyl, dimethylbutyl, and the like.
• Substituted alkyl groups are alkyl groups as described above which are substituted in one or more positions by, for example, halogens, oxo, hydroxy, C1-4-alkoxy, halogenated C1-4-alkoxy, and/or cyano.
• Halogens are preferred substituents, especially F and Cl.
• Alkoxy groups means alkyl-O— groups in which the alkyl portion is in accordance with the previous discussion. Suitable alkoxy groups are methoxy, ethoxy, propoxy and butoxy, pentoxy, hexoxy, heptoxy, octoxy and trifluoromethoxy. Preferred alkoxy groups are methoxy and ethoxy.
• alkoxycarbonyl means alkyl —O—CO— in which the alkyl portion is in accordance with the previous discussion. Examples include methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, and tert-butoxycarbonyl.
• Alkenyl refers to straight-chain or branched-chain aliphatic radicals containing 2 to 12 carbon atoms in which one or more —CH 2 —CH 2 — structures are each replaced by —CH ⁇ CH—.
• Suitable alkenyl groups are ethenyl, 1-propenyl, 2-methylethenyl, 1-butene, 2-butene, 1-pentenyl, and 2-pentenyl.
• Alkynyl refers to straight-chain or branched-chain aliphatic radicals containing 2 to 12 carbon atoms in which one or more —CH 2 —CH 2 — structures are each replaced by —C ⁇ C—.
• Suitable alkynyl groups are ethynyl, propynyl, 1-butynyl, and 2-butynyl.
• Cycloalkyl means a monocyclic, bicyclic or tricyclic nonaromatic saturated hydrocarbon radical.
• Cycloalkyl radicals for R 1 have 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms, especially 3 carbon atoms. Suitable cycloalkyl groups for R 1 include cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.
• Cycloalkyl radicals for R 2 have 3 to 12 carbon atoms, preferably 3 to 10 carbon atoms, especially 4 to 8 carbon atoms.
• Suitable cycloalkyl groups for R 2 include those listed above for R 1 as well as cycloheptyl, cyclooctyl, cyclononyl, norbornyl, 1-decalin, adamant-1-yl, and adamant-2-yl.
• Other suitable cycloalkyl groups for R 2 include spiro[2,4]heptyl, spiro[2.5]octyl, bicyclo[5.1.0]octyl, bicyclo[2.2.0]hexyl, spiro[3.3]heptyl, and bicyclo[4.2.0]octyl.
• the cycloalkyl group can be substituted.
• it can be substituted by halogens, C 1-4 -alkyls, C 1-4 -halogenated alkyls, C 1-4 -alkoxy and/or cyano.
• Cycloalkylalkyl refers to cycloalkyl-alkyl radicals in which the cycloalkyl and alkyl portions are in accordance with previous discussions. Suitable examples include cyclopropylmethyl and cyclopentylmethyl.
• Alkyl ethers refer to C 3 to C 12 alkoxyalkyl radicals. Suitable alkyl ether groups include methoxyethyl, ethoxyethyl, and methoxypropyl.
• Aryl as a group or substituent per se or as part of a group or substituent, refers to an aromatic carbocyclic radical containing 6 to 14 carbon atoms, preferably 6 to 12 carbon atoms, especially 6 to 10 carbon atoms.
• Suitable aryl groups include phenyl, naphthyl and biphenyl.
• Substituted aryl groups include the above-described aryl groups which are substituted one or more times by, for example, by halogen, C 1-4 -alkyl, C 1-4 -halogenated alkyl, hydroxy, C 1-4 -alkoxy, C 1-4 -halogenated alkoxy, nitro, methylenedioxy, ethylenedioxy, amino, C 1-4 -alkylamino, di-C 1-4 -alkylamino, C 1-4 -hydroxyalkyl, C 1-4 -hydroxyalkoxy, carboxy, cyano, C 2-4 -acyl, C 2-4 -alkoxycarbonyl, C 1-4 -alkylthio, C 1-4 -alkylsulphinyl, C 1-4 -alkylsulphonyl and phenoxy.
• Arylalkyl refers to an aryl-alkyl-radical in which the aryl and alkyl portions are in accordance with the previous descriptions.
• the aryl portion has 6 to 10 carbon atoms and the alkyl portion, which is straight-chained or branched, has 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms.
• the aryl portion can be substituted by the substituents described above for aryl groups and the alkyl portion can be substituted by oxo, halogens, cyano or combinations thereof. Suitable examples include benzyl, 1-phenethyl, 2-phenethyl, phenpropyl, fluorobenzyl, chlorobenzyl, methoxybenzyl, methylbenzyl and cyanobenzyl.
• Heteroaryl refers to an aromatic heterocyclic group having one or two rings and a total number of 5 to 10 ring atoms wherein at least one of the ring atoms is a heteroatom.
• the heteroaryl group contains 1 to 3, especially 1 or 2, hetero-ring atoms which are selected from N, O and S.
• Suitable heteroaryl groups include furyl, thienyl, pyrrolyl, pyrazolyl, imidazolyl, triazolyl, tetrazolyl, isoxazolyl, oxazolyl, thiazolyl, isothiazolyl, oxadiazolyl, oxatriazolyl, thiadiazolyl, pyridyl, pyridazinyl, pyrimidinyl, benzofuranyl, isobenzofuranyl, thionaphthenyl, isothionaphthenyl, indolyl, isoindolyl, indazolyl, benzisoxazolyl, benzoxazolyl, benzthiazolyl, benzisothiazolyl, purinyl, benzopyranyl, quinolinyl, isoquinolinyl, cinnolinyl, quinazolinyl, naphth
• Substituted heteroaryl refers to the heteroaryl groups described above which are substituted in one or more places by, for example, halogen, hydroxyl, aryl, alkyl, alkoxy, carboxy, methylene, cyano, trifluoromethyl, nitro, oxo, amino, alkylamino, and dialkylamino.
• Heteroarylalkyl refers to a heteroaryl-alkyl-group wherein the heteroaryl and alkyl portions are in accordance with the previous discussions. Suitable examples are pyridylmethyl, thienylmethyl, pyrimidinylmethyl, pyrazinylmethyl, and isoquinolinylmethyl.
• Heterocycles are non-aromatic cyclic groups containing at least one hetero-ring atom, preferably selected from N, S and O, for example, 3-tetrahydrofuranyl, piperidinyl, imidazolinyl, imidazolidinyl, pyrrolinyl, pyrrolidinyl, morpholinyl, piperazinyl, and indolinyl.
• Heterocycle-alkyl refers to a heterocycle-alkyl-group wherein the heterocyclic and alkyl portions are in accordance with the previous discussions. Suitable examples are piperidinyl-ethyl and pyrrolinyl-methyl.
• Carbocycles are non-aromatic monocyclic or bicyclic structures containing 5 to 14 carbon atoms, preferably 6 to 10 carbon atoms. Suitable examples are cyclopentenyl, cyclohexenyl, cyclohexadienyl, tetrahydronaphthenyl and indan-2-yl.
• Acyl refers to alkanoyl radicals having 1 to 6 carbon atoms in which the alkyl portion can be substituted by halogen, alkyl, aryl and/or alkoxy, or aroyl radicals having 7 to 15 carbon atoms in which the aryl portion can be substituted by, for example, halogen, alkyl and/or alkoxy.
• Suitable acyl groups include formyl, acetyl, propionyl, butanoyl and benzoyl.
• Substituted radicals preferably have 1 to 3 substituents, especially 1 to 2 substituents.
• R 1 is preferably H, alkyl such as methyl, ethyl and isopropyl, substituted alkyl, such as HOCH 2 CH 2 —, cycloalkyl such as cyclopropyl, cyclobutyl, and cyclopentyl, cycloalkylalkyl such as cyclopropylmethyl.
• R 1 is preferably methyl, ethyl or cycloalkyl such as cyclopropyl, cyclobutyl, or cyclopentyl, especially methyl, ethyl and cyclopropyl.
• R 2 is preferably cycloalkyl, aryl, heteroaryl, carbocycle or heterocycle.
• R 2 is preferably cycloalkyl such as cyclopentyl, cyclohexyl, cycloheptyl and norbornyl, aryl such as phenyl which is unsubstituted or substituted one or more times by, e.g., halogen, methoxy, nitro, cyano, amino or combinations thereof, heteroaryl such as pyridinyl, pyrimidinyl, thienyl, quinolinyl, and furanyl which is unsubstituted or substituted by, for example, methoxy and/or methylthio, carbocycle such as substituted or unsubstituted 2-indanyl, or heterocycle such as substituted or unsubstituted piperidinyl, pyrrolydinyl, and tetrahydrofuranyl.
• R 2 is aryl substituted by —CO—NH—SO 2 —R 5
• the aryl group is preferably phenyl and R 5 is preferably alkyl (e.g., methyl and ethyl), phenyl, thienyl, benzothienyl, benzothiazolyl, or pyridyl, which in each case is substituted or unsubstituted.
• R 2 is aryl substituted by —SO 2 —NH—CO—R 5
• the aryl group is preferably phenyl and R 5 is preferably alkyl (e.g., methyl and ethyl), phenyl, thienyl, benzothienyl, benzothiazolyl, or pyridyl, which in each case is substituted or unsubstituted.
• PDE4 inhibitors in accordance with the invention, are compounds described by subformulas Ia-If, which correspond to formula I, but exhibit the following preferred groups:
• preferred PDE4 inhibitors are compounds described by subformulas I′a-I′e, which correspond to formula I′, but exhibit the following preferred groups:
• Preferred aspects include pharmaceutical compositions comprising a compound of this invention and a pharmaceutically acceptable carrier and, optionally, another active agent as discussed below; a method of inhibiting a PDE4 enzyme, especially an isoenzyme, e.g., as determined by a conventional assay or one described herein, either in vitro or in vivo (in an animal, e.g., in an animal model, or in a mammal or in a human); a method of treating neurological syndrome, e.g., loss of memory, especially long-term memory, cognitive impairment or decline, memory impairment, etc.; a method of treating a disease state modulated by PDE4 activity, in a mammal, e.g., a human, e.g., those mentioned herein.
• a method of inhibiting a PDE4 enzyme especially an isoenzyme, e.g., as determined by a conventional assay or one described herein, either in vitro or in vivo (in an animal, e.g.
• the compounds of the present invention may be prepared conventionally. Some of the processes which can be used are described below. All starting materials are known or can be conventionally prepared from known starting materials.
• 2-Substituted hypoxanthines are produced by standard methods in the art, such as by neat reaction between 4-amino-5-imidazolecarboxamide and 2,2,2-trifluoroacetamide (E. Richter et al, J. Am. Chem. Soc . 1960, 82, 3144-3146; or A. Giner—Sorala, et al, J. Am. Chem. Soc . 1958, 80, 5744-5752; or A. Parkin, et al, J. Heterocycl. Chem . 1982, 19, 33-40). 6-Halo-2-trifluoromethylpurine may be prepared by methods common in the art (see J.-J. Bourguignon, et al., J. Med. Chem.
• 6-chloro-2-trifluoromethylpurine with either an alkyl halide, cycloalkyl halide, cycloalkylalkyl halide, heteroaryl halide or arylalkyl halide in a polar aprotic solvent such as N,N-dimethylforamide, dimethylsulfoxide, or dimethoxyethane in the presence of a base (e.g. K 2 CO 3 , Na 2 CO 3 , NaH) provides a mixture of 9- and 7-substituted 6-halopurines.
• a base e.g. K 2 CO 3 , Na 2 CO 3 , NaH
• phase transfer catalyst for example, 18-crown-6 or tetrabutylammonium chloride
• reaction temperature e.g. 60° C. to 150° C.
• reaction of a 6-halopurine under Mitsunobu conditions with an alkyl alcohol, cycloalkyl alcohol, arylalkyl alcohol, heteroaryl alcohol, or cycloalkylalkyl alcohol provides a mixture of 9- and 7-substituted 6-halopurines.
• the 9- and 7-isomers produced by the reactions described above are readily separated by chromatography.
• Such 9-substituted-6-halopurines undergo reaction with amines (e.g., ammonia, alkylamines, cycloalkylamines, or cycloalkylalkylamines) to provide adenine derivatives of Formula I and Formula I′.
• amines e.g., ammonia, alkylamines, cycloalkylamines, or cycloalkylalkylamines
• 6-halo-2-substituted purines readily undergo reaction with amines (e.g., ammonia, alkylamines, cycloalkylamines, or cycloalkylalkylamines) in the presence of polar protic solvents (e.g., methanol, ethanol, propanol etc.) to yield 6-N-substituted adenine analogs.
• amines e.g., ammonia, alkylamines, cycloalkylamines, or cycloalkylalkylamines
• polar protic solvents e.g., methanol, ethanol, propanol etc.
• a phase transfer catalyst for example, 18-crown-6 or tetrabutylammonium chloride
• reaction of 6-N-substituted adenines under Mitsunobu conditions with an alkyl alcohol, cycloalkyl alcohol, arylalkyl alcohol, heteroaryl alcohol, or cycloalkylalkyl alcohol provides 9-substituted 6-N-substituted adenines of Formula I and Formula I′.
• 6-N-Substituted-9-aryl- and 9-heteroaryl-adenines may be synthesized by methods common to the art, such as by reaction of a 4,6-dichloro-5-aminopyrimidine with an appropriately substituted aniline or heteroarylamine as described by J. L. Kelley et. al., J. Med. Chem ., 1997, 40, 3207 to produce 4-arylamino or 4-heteroarylamino-6-chloropyrimidines.
• Cyclization by treating with triethylorthoformate in the presence of an acid catalyst provides 6-choro-9-aryl- or 9-heteroaryl-purines, which can be derivatized at the 6-N-position as described above to provide adenine derivatives of Formula I and Formula I′.
• an acid catalyst e.g., ethylsulfonic acid
• 6-N-substituted adenines may undergo a coupling reaction with arylboronic acids or heteroarylboronic acids in the presence of a base (e.g., triethylamine, pyridine, N—
• a base e.g., triethylamine, pyridine, N—
• methylmorpholine a copper catalyst (e.g., Cu(OAc) 2 ), and a polar aprotic solvent (e.g. dichloromethane, 1,4-dioxane, THF, DMF, CH 3 CN) in a modoified manner as described previously for the N-arylation of imidazole and pyrazole (see, P. Y. S. Lam et. al. Tetrahedron Lett. 1998, 39, 2941-2944) to generate 9-aryl- or 9-heteroaryl-adenines of Formula I and Formula I′.
• a polar aprotic solvent e.g. dichloromethane, 1,4-dioxane, THF, DMF, CH 3 CN
• certain halogenated aryl and heteroaryl substrates can undergo aromatic nucleophilic substitution reaction with 6-(substituted)amino-2-trifluoromethylpurine in a polar aprotic solvent (e.g., DMF or DMSO) using a base (e.g., cesium carbonate) to provide target 9-aryl or 9-heteroarylpurines.
• a polar aprotic solvent e.g., DMF or DMSO
• a base e.g., cesium carbonate
• Certain halogenated aryl and heteroaryl substrates can undergo aromatic nucleophilic substitution reactions with 6-substituted-2-trifluoromethylpurines in a polar aprotic solvent (e.g., DMF or DMSO) using a base (e.g., cesium carbonate or potassium carbonate) to provide heteroarylpurines.
• a polar aprotic solvent e.g., DMF or DMSO
• a base e.g., cesium carbonate or potassium carbonate
• reaction of a 6-N-substituted-2-trifluoromethylpurine with 4-chloro-2-methylthiopyrimidine in the presence of K 2 CO 3 in DMF provides 6-N-substituted-2-trifluoromethyl-9-(4-(2-methylthio)pyrimidinyl)purine.
• methylsulfone Oxidation of the methylthio moiety with a suitable oxidizing agent such as mcpba provides the methylsulfoxide derivative with one equivalent of oxidizing agent and with 2 or more equivalents, the methylsulfone is formed as depicted in the scheme above.
• the methylsulfone is a suitable leaving group (as would be a halogen or other sulfones) and as such undergoes nucleophilic substitution reactions with amines (e.g., methylamine, dimethylamine, morpholine, cyclopropylamine, aniline, etc.) to provide additional desired adenine compounds of Formula I and Formula I′.
• amines e.g., methylamine, dimethylamine, morpholine, cyclopropylamine, aniline, etc.
• the optical isomers can be obtained by resolution of the racemic mixtures according to conventional processes, for example, by the formation of diastereoisomeric salts using an optically active acid or base or formation of covalent diastereomers.
• appropriate acids are tartaric, diacetyltartaric, dibenzoyltartaric, ditoluoyltartaric and camphorsulfonic acid.
• Mixtures of diastereoisomers can be separated into their individual diastereomers on the basis of their physical and/or chemical differences by methods known to those skilled in the art, for example, by chromatography or fractional crystallization.
• the optically active bases or acids are then liberated from the separated diastereomeric salts.
• a different process for separation of optical isomers involves the use of chiral chromatography (e.g., chiral HPLC columns), with or without conventional derivation, optimally chosen to maximize the separation of the enantiomers.
• Suitable chiral HPLC columns are manufactured by Diacel, e.g., Chiracel OD and Chiracel OJ among many others, all routinely selectable.
• Enzymatic separations, with or without derivitization, are also useful.
• the optically active compounds of Formula I or Formula I′ can likewise be obtained by chiral syntheses utilizing optically active starting materials.
• the compounds can be used in different enriched isotopic forms, e.g., enriched in the content of 2 H, 3 H, 11 C, 13 C and/or 14 C.
• the compounds are deuterated. Such deuterated forms can be made the procedure described in U.S. Pat. No. 6,334,997.
• the present invention also relates to useful forms of the compounds as disclosed herein, such as pharmaceutically acceptable salts and prodrugs of all the compounds of the present invention.
• Pharmaceutically acceptable salts include those obtained by reacting the main compound, functioning as a base, with an inorganic or organic acid to form a salt, for example, salts of hydrochloric acid, sulfuric acid, phosphoric acid, methane sulfonic acid, camphor sulfonic acid, oxalic acid, maleic acid, succinic acid and citric acid.
• Pharmaceutically acceptable salts also include those in which the main compound functions as an acid and is reacted with an appropriate base to form, e.g., sodium, potassium, calcium, mangnesium, ammonium, and choline salts.
• acid addition salts of the claimed compounds may be prepared by reaction of the compounds with the appropriate inorganic or organic acid via any of a number of known methods.
• alkali and alkaline earth metal salts are prepared by reacting the compounds of the invention with the appropriate base via a variety of known methods.
• acid salts that can be obtained by reaction with inorganic or organic acids: acetates, adipates, alginates, citrates, aspartates, benzoates, benzenesulfonates, bisulfates, butyrates, camphorates, digluconates, cyclopentanepropionates, dodecylsulfates, ethanesulfonates, glucoheptanoates, glycerophosphates, hemisulfates, heptanoates, hexanoates, fumarates, hydrobromides, hydroiodides, 2-hydroxy-ethanesulfonates, lactates, maleates, methanesulfonates, nicotinates, 2-naphthalenesulfonates, oxalates, palmoates, pectinates, persulfates, 3-phenylpropionates, picrates, pivalates, propionates,
• the salts formed are pharmaceutically acceptable for administration to mammals.
• pharmaceutically unacceptable salts of the compounds are suitable as intermediates, for example, for isolating the compound as a salt and then converting the salt back to the free base compound by treatment with an alkaline reagent.
• the free base can then, if desired, be converted to a pharmaceutically acceptable acid addition salt.
• the compounds of the invention can be administered alone or as an active ingredient of a formulation.
• the present invention also includes pharmaceutical compositions of compounds of Formula I or Formula I′ containing, for example, one or more pharmaceutically acceptable carriers.
• the compounds of the present invention can be administered to anyone requiring or desiring PDE4 inhibition, and/or enhancement of cognition. Administration may be accomplished according to patient needs, for example, orally, nasally, parenterally (subcutaneously, intraveneously, intramuscularly, intrasternally and by infusion), by inhalation, rectally, vaginally, topically, locally, transdermally, and by ocular administration.
• solid oral dosage forms can be used for administering compounds of the invention including such solid forms as tablets, gelcaps, capsules, caplets, granules, lozenges and bulk powders.
• the compounds of the present invention can be administered alone or combined with various pharmaceutically acceptable carriers, diluents (such as sucrose, mannitol, lactose, starches) and excipients known in the art, including but not limited to suspending agents, solubilizers, buffering agents, binders, disintegrants, preservatives, colorants, flavorants, lubricants and the like.
• Time release capsules, tablets and gels are also advantageous in administering the compounds of the present invention.
• liquid oral dosage forms can also be used for administering compounds of the invention, including aqueous and non-aqueous solutions, emulsions, suspensions, syrups, and elixirs.
• dosage forms can also contain suitable inert diluents known in the art such as water and suitable excipients known in the art such as preservatives, wetting agents, sweeteners, flavorants, as well as agents for emulsifying and/or suspending the compounds of the invention.
• the compounds of the present invention may be injected, for example, intravenously, in the form of an isotonic sterile solution. Other preparations are also possible.
• Suppositories for rectal administration of the compounds of the present invention can be prepared by mixing the compound with a suitable excipient such as cocoa butter, salicylates and polyethylene glycols.
• a suitable excipient such as cocoa butter, salicylates and polyethylene glycols.
• Formulations for vaginal administration can be in the form of a pessary, tampon, cream, gel, paste, foam, or spray formula containing, in addition to the active ingredient, such suitable carriers as are known in the art.
• the pharmaceutical composition can be in the form of creams, ointments, liniments, lotions, emulsions, suspensions, gels, solutions, pastes, powders, sprays, and drops suitable for administration to the skin, eye, ear or nose. Topical administration may also involve transdermal administration via means such as transdermal patches.
• Aerosol formulations suitable for administering via inhalation also can be made.
• the compounds according to the invention can be administered by inhalation in the form of a powder (e.g., micronized) or in the form of atomized solutions or suspensions.
• the aerosol formulation can be placed into a pressurized acceptable propellant.
• the compounds can be administered as the sole active agent or in combination with other pharmaceutical agents such as other agents used in the treatment of cognitive impairment and/or in the treatment of psychosis, e.g., other PDE4 inhibitors, calcium channel blockers, chloinergic drugs, adenosine receptor modulators, amphakines NMDA-R modulators, mGluR modulators, and cholinesterase inhibitors (e.g., donepezil, rivastigimine, and glanthanamine).
• each active ingredient can be administered either in accordance with their usual dosage range or a dose below its usual dosage range.
• the present invention further includes methods of treatment that involve inhibition of PDE4 enzymes.
• the present invention includes methods of selective inhibition of PDE4 enzymes in animals, e.g., mammals, especially humans, wherein such inhibition has a therapeutic effect, such as where such inhibition may relieve conditions involving neurological syndromes, such as the loss of memory, especially long-term memory.
• Such methods comprise administering to an animal in need thereof, especially a mammal, most especially a human, an inhibitory amount of a compound, alone or as part of a formulation, as disclosed herein.
• the condition of memory impairment is manifested by impairment of the ability to learn new information and/or the inability to recall previously learned information.
• Memory impairment is a primary symptom of dementia and can also be a symptom associated with such diseases as Alzheimer's disease, schizophrenia, Parkinson's disease, Huntington's disease, Pick's disease, Creutzfeld-Jakob disease, HIV, cardiovascular disease, and head trauma as well as age-related cognitive decline.
• Dementias are diseases that include memory loss and additional intellectual impairment separate from memory.
• the present invention includes methods for treating patients suffering from memory impairment in all forms of dementia.
• Dementias are classified according to their cause and include: neurodegenerative dementias (e.g., Alzheimer's, Parkinson's disease, Huntington's disease, Pick's disease), vascular (e.g., infarcts, hemorrhage, cardiac disorders), mixed vascular and Alzheimer's, bacterial meningitis, Creutzfeld-Jacob Disease, multiple sclerosis, traumatic (e.g., subdural hematoma or traumatic brain injury), infectious (e.g., HIV), genetic (down syndrome), toxic (e.g., heavy metals, alcohol, some medications), metabolic (e.g., vitamin B12 or folate deficiency), CNS hypoxia, Cushing's disease, psychiatric (e.g., depression and schizophrenia), and hydrocephalus.
• neurodegenerative dementias e.g., Alzheimer
• the present invention includes methods for dealing with memory loss separate from dementia, including mild cognitive impairment (MCI) and age-related cognitive decline.
• MCI mild cognitive impairment
• the present invention includes methods of treatment for memory impairment as a result of disease.
• the invention includes methods for dealing with memory loss resulting from the use of general anesthetics, chemotherapy, radiation treatment, post-surgical trauma, and therapeutic intervention.
• the compounds may be used to treat psychiatric conditions including schizophrenia, bipolar or manic depression, major depression, and drug addiction and morphine dependence. These compounds may enhance wakefulness.
• PDE4 inhibitors can be used to raise cAMP levels and prevent neurons from undergoing apoptosis. PDE4 inhibitors are also known to be anti-inflammatory. The combination of anti-apoptotic and anti-inflammatory properties make these compounds useful to treat neurodegeneration resulting from any disease or injury, including stroke, spinal cord injury, neurogenesis, Alzheimer's disease, multiple sclerosis, amylolaterosclerosis (ALS), and multiple systems atrophy (MSA).
• the present invention includes methods of treating patients suffering from memory impairment due to, for example, Alzheimer's disease, schizophrenia, Parkinson's disease, Huntington's disease, Pick's disease, Creutzfeld-Jakob disease, depression, aging, head trauma, stroke, CNS hypoxia, cerebral senility, multiinfarct dementia and other neurological conditions including acute neuronal diseases, as well as HIV and cardiovascular diseases, comprising administering an effective amount of a compound according to Formula I or Formula I′ or pharmaceutically acceptable salts thereof.
• the compounds of the present invention can also be used in a method of treating patients suffering from disease states characterized by decreased NMDA function, such as schizophrenia.
• the compounds can also be used to treat psychosis characterized by elevated levels of PDE 4, for example, various forms of depression, such as manic depression, major depression, and depression associated with psychiatric and neurological disorders.
• the compounds of the invention also exhibit anti-inflammatory activity.
• inventive compounds are useful in the treatment of a variety of allergic and inflammatory diseases, particularly disease states characterized by decreased cyclic AMP levels and/or elevated phosphodiesterase 4 levels.
• a method of treating allergic and inflammatory disease states comprising administering an effective amount of a compound according to Formula I or Formula I′ or a pharmaceutically acceptable salt thereof.
• Such disease states include: asthma, chronic bronchitis, chronic obstructive pulmonary disease (COPD), atopic dermatitis, urticaria, allergic rhinitis, allergic conjunctivitis, vernal conjunctivitis, esoniophilic granuloma, psoriasis, inflammatory arthritis, rheumatoid arthritis, septic shock, ulcerative colitis, Crohn's disease, reperfusion injury of the myocardium and brain, chronic glomerulonephritis, endotoxic shock, adult respiratory distress syndrome, cystic fibrosis, arterial restenosis, artherosclerosis, keratosis, rheumatoid spondylitis, osteoarthritis, pyresis, diabetes mellitus, pneumoconiosis, chronic obstructive airways disease, chronic obstructive pulmonary disease, toxic and allergic contact eczema, atopic eczema,
• PDE4 inhibitors for treating asthma, chronic bronchitis, psoriasis, allergic rhinitis, and other inflammatory diseases, and for inhibiting tumor necrosis factor are known within the art. See, e.g., WO 98/58901, JP11-18957, JP 10-072415, WO 93/25517, WO 94/14742, U.S. Pat. No. 5,814,651, and U.S. Pat. No. 5,935,978. These references also describe assays for determining PDE4 inhibition activity, and methods for synthesizing such compounds. The entire disclosures of these documents are hereby incorporated by reference.
• PDE4 inhibitors may be used to prevent or ameliorate osteoporosis, as an antibiotic, for treatment of cardiovascular disease by mobilizing cholesterol from atherosclerotic lesions, to treat rheumatoid arthritis (RA), for long-term inhibition of mesenchymal-cell proliferation after transplantation, for treatment of urinary obstruction secondary to benign prostatic hyperplasia, for suppression of chemotaxis and reduction of invasion of colon cancer cells, for treatment of B cell chronic lymphocytic leukemia (B-CLL), for inhibition of uterine contractions, to attenuate pulmonary vascular ischemia-reperfuision injury (IRI), for corneal hydration, for inhibition of IL-2R expression and thereby abolishing HIV-1 DNA nuclear import into memory T cells, for augmentation of glucose-induced insulin secretion, in both the prevention and treatment of colitis, and to inhibit mast cell degranulation.
• RA rheumatoid arthritis
• RA rheumatoid arthritis
• the compounds of the present invention can be administered as the sole active agent or in combination with other pharmaceutical agents such as other agents used in the treatment of cognitive impairment and/or in the treatment of psychosis, e.g., other PDE4 inhibitors, calcium channel blockers, chloinergic drugs, adenosine receptor modulators, amphakines NMDA-R modulators, mGluR modulators, and cholinesterase inhibitors (e.g., donepezil, rivastigimine, and glanthanamine).
• each active ingredient can be administered either in accordance with their usual dosage range or a dose below their usual dosage range.
• the dosages of the compounds of the present invention depend upon a variety of factors including the particular syndrome to be treated, the severity of the symptoms, the route of administration, the frequency of the dosage interval, the particular compound utilized, the efficacy, toxicology profile, pharmacokinetic profile of the compound, and the presence of any deleterious side-effects, among other considerations.
• the compounds of the invention are typically administered at dosage levels and in a mammal customary for PDE4 inhibitors such as those known compounds mentioned above.
• the compounds can be administered, in single or multiple doses, by oral administration at a dosage level of, for example, 0.01-100 mg/kg/day, preferably 0.1-70 mg/kg/day, especially 0.5-10 mg/kg/day.
• Unit dosage forms can contain, for example, 0.1-50 mg of active compound.
• the compounds can be administered, in single or multiple dosages, at a dosage level of, for example, 0.001-50 mg/kg/day, preferably 0.001-10 mg/kg/day, especially 0.01-1 mg/kg/day.
• Unit dosage forms can contain, for example, 0.1-10 mg of active compound.
• buffers, media, reagents, cells, culture conditions and the like are not intended to be limiting, but are to be read so as to include all related materials that one of ordinary skill in the art would recognize as being of interest or value in the particular context in which that discussion is presented. For example, it is often possible to substitute one buffer system or culture medium for another and still achieve similar, if not identical, results. Those of skill in the art will have sufficient knowledge of such systems and methodologies so as to be able, without undue experimentation, to make such substitutions as will optimally serve their purposes in using the methods and procedures disclosed herein.
• a 1 L round-bottom flask (three neck) containing 340 g of trifluoroacetamide was heated in an oil bath at 110° C. After the trifluoroacetamide melted, 50 g of 5-aminoimidazole-4-carboxamide-HCl was added. The mixture was warmed to reflux (bath temp 160 to 165° C.) for 4 hours, cooled to room temperature, and the rocky solid was triturated with 1 L of ether. The ether was decanted off and the remaining solid was warmed until melted and 200 mL of ether was introduced by a dropping-funnel through a water-cooled condenser. The mixture was cooled to room temperature and an additional 200 mL of ether was added with stirring.
• methansulphonate salt (mesylate salt)
• 4 ml of 0.1N CH 3 SO 3 H in EtOAc was added to a solution of 145 mg (0.4 mmol) 6-cyclopropylamino-9-(2-fluorobenzyl)-2-trifluoromethylpurine in EtOAc.
• 1 ml of hexane was added to a warm solution and the resultant mixture was allowed to crystallize (within a refrigerator).
• the solid was collected to give 148 mg of the mesylate salt.
• the salt was relatively insoluble in H 2 O. M.p. 167.5-169.0 C; m.p. 114-118 C for free base.
• 6-methylamino-9-[4-(2-methylthiopyrimidino)]-2-trifluoromethylpurine was made by the same procedure.
• 6-Cyclopropylamino-9-(4-methoxycarbonylphenyl)-2-trifluoromethylpurine (20 mg, 0.053 mmol) was treated with 0.53 mmol of 1-2 M KOH in methanol (containing 5% water) and stirred for 14 hours at room temperature.
• the residue was extracted with 20% methanol in dichloromethane.
• the extraction was loaded on a silica gel column and eluted with 20% methanol in dichloromethane to give 9-(4-carboxyphenyl)-6-cyclopropylamino-2-trifluoromethylpurine (14 mg, 70% yield).
• 6-Cyclopropylamino-9-(2-methylsulfonypyrimidin-4-yl)-2-trifluoromethylpurine (12 mg, 0.03 mmol) in 3 ml of tetrahydrofuran was treated with methylmagnesium iodide (0.045 mmol of 3.0 M solution in ethyl ether) at ambient temperature and stirred for four hours. Ethyl acetate (20 ml) was added followed by 5% sodium bicarbonate (20 ml). The organic layer was isolated and concentrated under vacuum.
• Human PDE4 was obtained from baculovirus-infected Sf9 cells that expressed the recombinant enzyme.
• the cDNA encoding hPDE-4D6 was subcloned into a baculovirus vector.
• Insect cells (Sf9) were infected with the baculovirus and cells were cultured until protein was expressed.
• the baculovirus-infected cells were lysed and the lysate was used as source of hPDE-4D6 enzyme.
• the enzyme was partially purified using a DEAE ion exchange chromatography. This procedure can be repeated using cDNA encoding other PDE-4 enzymes.
• Type 4 phosphodiesterases convert cyclic adenosine monophosphate (cAMP) to 5′-adenosine monophosphate (5′-AMP).
• Nucleotidase converts 5′-AMP to adenosine. Therefore the combined activity of PDE4 and nucleotidase converts cAMP to adenosine.
• Adenosine is readily separated from cAMP by neutral alumina columns.
• Phosphodiesterase inhibitors block the conversion of cAMP to adenosine in this assay; consequently, PDE4 inhibitors cause a decrease in adenosine.
• Cell lysates (40 ul) expressing hPDE-4D6 were combined with 50 ul of assay mix and 10 ul of inhibitors and incubated for 12 min at room temperature. Final concentrations of assay components were: 0.4 ug enzyme, 10 mM Tris-HCl (pH 7.5), 10 mM MgCl 2 , 3 uM cAMP, 0.002 U 5′-nucleotidase, and 3 ⁇ 10 4 cpm of [3H]cAMP.
• the reaction was stopped by adding 100 ⁇ l of boiling 5 mN HCl. An aliquot of 75 ⁇ l of reaction mixture was transferred from each well to alumina columns (Multiplate; Millipore).
• adenosine was eluted into an OptiPlate by spinning at 2000 rpm for 2 min; 150 ⁇ l per well of scintillation fluid was added to the OptiPlate. The plate was sealed, shaken for about 30 min, and cpm of [ 3 H]adenosine was determined using a Wallac Trilux®.
• test compounds are dissolved in 100% DMSO and diluted into the assay such that the final concentration of DMSO is 0.1%. DMSO does not affect enzyme activity at this concentration.
• pIC 50 values were determined by screening 6 to 12 concentrations of compound ranging from 0.1 nM to 10,000 nM and then plotting drug concentration versus 3 H-adenosine concentration. Nonlinear regression software (Assay Explorer®) was used to estimate pIC 50 values.
• the test was performed as previously described (Zhang, H.-T., Crissman, A. M., Dorairaj, N. R., Chandler, L. J., and O'Donnell, J. M., Neuropsychopharmacology , 2000, 23, 198-204.).
• the apparatus (Model E10-16SC, Coulbourn Instruments, Allentown, Pa.) consisted of a two-compartment chamber with an illuminated compartment connected to a darkened compartment by a guillotine door.
• the floor of the darkened compartment consisted of stainless steel rods through which an electric foot-shock could be delivered from a constant current source. All experimental groups were first habituated to the apparatus the day before the start of the experiment.
• the rat (Male Spraque-Dawley (Harlan) weighing 250 to 350 g) was placed in the illuminated compartment facing away from the closed guillotine door for 1 minute before the door was raised. The latency for entering the darkened compartment was recorded. After the rat entered the darkened compartment, the door was closed and a 0.5 mA electric shock was administered for 3 seconds. Twenty-four hours later, the rat was administered 0.1 mg/kg MK-801 or saline, 30 minutes prior to the injection of saline or test compound (dosed from 0.1 to 2.5 mg/kg, i.p.), which was 30 minutes before the retention test started. The rat was again placed in the illuminated compartment with the guillotine door open. The latency for entering the darkened compartment was recorded for up to 180 seconds, at which time the trial was terminated.
• mice Male Spraque-Dawley (Harlan) weighing 250 to 350 g were placed in the eight-arm radial maze (each arm was 60 ⁇ 10 ⁇ 12 cm high; the maze was elevated 70 cm above the floor) for acclimation for two days.
• Rats were then placed individually in the center of the maze for 5 minutes with food pellets placed close to the food wells, and then, the next day, in the wells at the end of the arms; 2 sessions a day were conducted. Next, four randomly selected arms were then baited with one pellet of food each. The rat was restricted to the center platform (26 cm in diameter) for 15 seconds and then allowed to move freely throughout the maze until it collected all pellets of food or 10 minutes passed, whichever came first.
• test duration i.e., the time spent in the collection of all the pellets in the maze. If the working memory error was zero and the average reference memory error was less than one in five successive trials, the rats began the drug tests. MK-801 or saline was injected 15 minutes prior to vehicle or test agent, which was given 45 minutes before the test. Experiments were performed in a lighted room, which contained several extra-maze visual cues.
• MK-801 0.1 mg/kg, i.p.
• MK-801 increased the frequencies of both working and reference memory errors (p ⁇ 0.01). This amnesic effect of MK-801 on working memory is reversed in a statistically significant manner by the administration of actual test compounds in a dose-dependent fashion.

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